The complaint, filed by the Justice Department in the U.S. District Court for the Northern District of Illinois, seeks to block the enforcement of state and local policies that the Trump administration says obstruct federal immigration enforcement. Sanctuary laws prevent local authorities from cooperating with federal immigration officers.

DOJ lawyers said multiple Illinois laws, including the Way Forward Act, TRUST Act, Welcoming City Act, and Cook County Ordinance 11-O-73, violate the supremacy clause of the Constitution because they prevent state and local officials from cooperating with federal immigration authorities, according to the 28-page complaint.

The lawsuit came just one day after Attorney General Pam Bondi took office with a vow to prioritize immigration enforcement, including by cutting off federal funding to sanctuary cities that don’t cooperate with DOJ.

Trump administration’s legal argument

President Donald Trump declared a national emergency on Inauguration Day, citing an “unprecedented ‘illegal entry of aliens’ into” the country, the suit states.

The lawsuit asserts that sanctuary policies in Chicago and Illinois “deliberately obstruct” federal law enforcement efforts, leading to the release of dangerous criminals into communities instead of their transfer to Immigration and Customs Enforcement custody.

Some of those hurdles include Chicago’s Welcoming City Ordinance, which bars local law enforcement from cooperating with ICE, a Cook County policy that refuses to comply with federal detainer requests without a prior reimbursement agreement with ICE, and a state law that similarly hinders cooperation with the agency.

The lawsuit also cites a piece of recent federal legislation, the Laken Riley Act, which mandates the detention of illegal immigrants accused of crimes such as theft, burglary, or assaulting a law enforcement officer. The Trump administration argued that Chicago and Illinois policies make it nearly impossible for ICE to carry out this federal mandate.

Illinois and Chicago’s defense of sanctuary policies

Illinois and Chicago officials have previously defended their sanctuary laws, arguing they protect immigrant communities and foster trust between police and residents. Gov. JB Pritzker (D-IL) recently said while he supports deportation for violent criminals, he does not want local police to act as federal immigration agents.

The city of Chicago has said limiting cooperation with ICE prevents racial profiling and encourages immigrants to report crimes without fear of deportation.

Next steps

The lawsuit seeks injunctive relief to halt enforcement of the sanctuary laws, arguing they hinder the federal government’s ability to enforce immigration policies.

If successful, the case could set a precedent for future legal challenges against other sanctuary jurisdictions nationwide.